1. Field of the Invention
The present invention relates to a rue nozzle for a combustion engine, and preferably a low pressure fuel injection nozzle.
The injection under pressure of the fuel necessary for operation at a particular predetermined point of the combustion engine has been known for a long time, initially for diesel engines and then for Otto engines. This can be fuel injection into a space downstream of the inlet valve. For Otto engines, injection onto the inlet valve or into the intake pipe upstream of the inlet valve is also customary.
There are attempts being made to configure and operate an injection nozzle in such a way that it produces a finer aerosol than is otherwise customary and/or possible with an injection nozzle. In such injection nozzles, as is known from EP-A-36 617, ultrasonic vibration is additionally provided, as has already been known for a long time for ultrasonic liquid atomizers. For liquid atomization, the ultrasonic frequency to be employed necessarily lies in the range above 100 kHz. The precise frequency and the design of a respectively provided nozzle part vibrating at ultrasonic frequency are mutually dependent. The injection nozzle per se here produces a fuel jet which corresponds in shape to the structural configuration and the liquid constituents of which are then atomized by that part of the whole nozzle which is vibrating at ultrasonic frequency to form a flowing mist of droplets consisting of fine aerosol droplets. Much the same is evident to the person skilled in the art from JP-A-60 22 066.
The present invention is concerned with a development leading in another direction, namely with the provision of measures for the appropriate selection of the shape of the fuel jet.
All known fuel injection nozzles have a characteristic fuel jet shape predetermined by their construction. As is known, the shape of the fuel jet is important for the formation of the air/fuel mixture, not only with respect to minimum specific fuel consumption but also with respect to environmental pollution by unwanted exhaust-gas components which are formed, and important for the smoothness of running of the engine. A distinction is drawn, for example, between a fuel injection nozzle which produces a concentrated jet and a nozzle which delivers a conical jet. Both shapes of jet have size distributions of the droplets of fuel sprayed from the nozzle which are characteristic of them and, moreover, among other things also different.
Different shapes of the fuel jet are optimal in each case depending on parameters of a particular combustion engine and the features of its construction and the particular load condition.